Add instructions and some other changes

Add following 16 bit instructions
All the Special data instructions and branch and exchange in <ARMv7-M
Architecture Reference Manual> Page159.
Add pesudocode in the above book like BranchTo, BranchWritePC etc.
Add a field 'mode' in struct armv7m_reg_t.
Change excute fucntion of cm3.
Add some reference books.